Proportional control

About: Proportional control is a research topic. Over the lifetime, 3756 publications have been published within this topic receiving 49050 citations.

Model-based control and estimation of cavity flow oscillations

Abstract: Techniques for feedback control of oscillations in the flow past a cavity are presented. Low-order models are obtained using two methods (empirical Galerkin models, and a simple nonlinear oscillator model), and validated against 2D direct numerical simulations of the flow, which is actuated by a body force at the leading edge of the cavity. The models are used to construct dynamic observers, which reconstruct the flow state from a single pressure sensor, and perform much better than static estimators commonly used for flow estimation. Several control approaches are compared, including simple proportional control with a phase lag, LQG control using Galerkin models, and a dynamic phasor approach based on the work of Noack et al (2003). All three controllers are implemented in the full simulation, and able to reduce the amplitude of oscillations. The LQG regulator requires careful tuning, and the closed-loop behavior often does not match that predicted by the model, but the dynamic phasor approach eliminates the oscillations completely in the full simulation, with a transient response that matches that predicted by the loworder model.

A new set-point controller with bounded torques for robot manipulators

Abstract: In this paper, we propose a simple controller for set-point control of robot manipulators. The structure of this controller is composed by a saturated proportional-saturated derivative feedback plus gravity compensation. Such a control scheme has two practical features. First, for all desired joint positions, this controller delivers torques inside prescribed limits according to the actuator capability and second, the steady-state position errors owing to static friction can be arbitrarily reduced. In the case of absence of friction, we show global asymptotic stability of the closed-loop system. The performance of the proposed controller is illustrated via experiments on a two-degrees-of-freedom (2-DOF) direct-drive robot system.

Stability analysis of nonlinear fuzzy PI control systems

Abstract: In this paper, we analyze the stability of nonlinear fuzzy PI (proportional-integral) control systems. The fuzzy PI controller involved is actually a nonlinear adaptive PI controller whose gains change continuously with output of the processes under control. We have employed the "small gain theorem" to obtain a simple sufficient condition for the global asymptotic stability of the nonlinear fuzzy PI control systems. In addition, we have proven that in a conventional PI control system, if the linear PI controller is replaced by the nonlinear fuzzy PI controller, then the stability of the resulting control system remains unchanged. This result is true no matter the given process is linear or not. We have also derived explicit formulas for the computation of the fuzzy PI controller parameters, using only the proportional and integral gains of the corresponding linear PI controller. >

Nonlinear adaptive robust control of hydraulic actuators regulated by proportional directional control valves with deadband and nonlinear flow gains

Abstract: This paper studies the motion control of single-rod hydraulic actuators regulated by proportional directional control (PDC) valves with deadband and nonlinear flow gains. The boom motion control of a hydraulic robot arm driven by a single-rod hydraulic actuator is used as a case study. The experimental system dynamics are highly nonlinear. In addition, the system has large extent of modeling uncertainties such as the variation of payload and friction forces. Furthermore, the PDC valve used to regulate the control flow rate to the hydraulic actuator has a large extent of deadband and a very nonlinear flow gain coefficient right out of the deadband region. These issues make the precision control of such a system difficult. To deal with these issues, the paper presents a discontinuous projection based adaptive robust controller. Direct inverse is used to compensate for the effect of the valve deadband, and certain straight-line approximations are used to model the nonlinear flow gain coefficient of the valve. The approximation error of the nonlinear flow mapping is deal with via certain robust feedback. Theoretically, the proposed adaptive robust control (ARC) guarantees a prescribed output tracking transient performance and final tracking accuracy while achieving asymptotic output tracking in the presence of parametric uncertainties. Comparative experimental results are presented to illustrate the proposed control algorithm and the practical difficulties in controlling such a complex nonlinear dynamic system.